Process for the epoxidation of unsaturated compounds

ABSTRACT

Olefinically unsaturated organic compounds are epoxidized with solutions of organic percarboxylic acid. An aqueous solution of the percarboxylic acid having at least 2 carbon atoms is dehydrated by extraction and/or distillation with the compound to be epoxidized. The dehydrated product is held at 30* - 100* C. and subjected to a subsequent reaction.

United States Patent 1191 Kleemann et al. 14 1 Jan. 2, 1973 [54] PROCESSFOR THE EPOXIDATION OF [56] References Cited NSATURATED MP UNDS U Co 0UNITED STATES PATENTS [75] Inventors: Axel Kleemann, Oberursel; Manfred2 903 465 9/1959 S I 260/348 5 L Kriiger Offenbach; Gel-d schreyel. utereta Grossauheim; Otto weiberg New 2,877,266 3/1959 Korach ..260/502 RIsenburg 2; Wolfgang Weigert, FOREIGN PATENTS OR APPLICATIONS fenbach,all of Germany l,083,797 6/1960 Germany Asslgnw Deulsche Gold u S he d975,715 11/1964 Great Britain ..260/502 R anstalt vormals Roessler,Frankfurt 594,167 3/1960 Canada ..260/502 R (Main), Germany PrimaryExaminerNorma S. Milestone [22] Filed 1970 Attorney-Cushman, Darby &Cushman [21] Appl. No.: 60,872

[57] ABSTRACT [30] Foreign Application Priority Data Olefinicallyunsaturated organic compounds are epoxidized with solutions of organicpercarboxylic acid. An Aug. 21, 1969 Germany ..P 19 42 557.1 aqueousSolution-Of the percarboxylic i i g at least 2 carbon atoms isdehydrated by extraction [52] US. Cl. ..260/348.5 L and/or distillationwith the com pound to be epox- [5l] Int. Cl ..C07d 1/06, C07d 1/08, C07dl/l6, idized The dehydrated product is held at I C07d C. and subjectedto a subsequent reaction. [58] Fleld of Search ..260/348.5 L, 502 R 6Claims, 1 Drawing Figure PROCESS FOR THE EPOXIDATION OF UNSATURATEDCOMPOUNDS The invention is concerned with a process of epoxidizingolefinically unsaturated (i.e., ethylenically unsaturated) compoundswhich are difficult to epoxidize.

It is known to convert materials having olefinically unsaturated doublebonds to the corresponding epoxides using water free solutions ofperacetic acid in a suitable inert solvent (see Frostick, et al., .lour.Amer. Chem. Soc. 81, 3350-6 (1959)). Although this process is used tothe greatest practicable extent in many cases long reaction times arerequired, especially with olefins that are difficultly epoxidizable, as,for example, esters or e'thers having an allylic double bond as well asolefins with a terminal double bond. Besides there must be madeallowance for unsatisfactory reactions and yields. In this case thepresence of the solvent necessary for the peracetic acid noticeablyreduces the concentration of the reaction and also must be againseparated and therefore represents a ballast.

It is also known toreact the epoxidizable liquid compoundscountercurrently with peracetic acid or perpropionic acid. The process,however, only proceeds favorably if the per acid is used in strongdilution with organic compounds such as acetic acid or in the presenceof acetaldehyde or an organic solvent such as acetone (Celanese, EnglishPat. No. 1,053,972). Otherwise the danger of explosion is too great.There fore the process is primarily operated with raw gases from theacetaldehyde oxidization (Kreisler, German Pat. No. 1,266,302 andCelanese British Pat. No.. 1,053,972).

has now been found that olefinically unsaturated, difficultlyepoxidizable water insoluble compounds can be epoxidized in anindustrially simple and less dangerous form with organic percarboxylicacids which contain at least two carbon atoms, if one proceeds with anaqueous solution of this per carboxylic acid and removes water with helpof the compounds to be epoxidized by extraction and/or azeotropicdistillation. The thus obtained water free solution of percarboxylicacid in the'excess unsaturated compound is then held at 30 100 C. untilthe desired reaction of percarboxylic acid with the olefinic compound toform the corresponding epoxide is obtained. Preferably the reaction iscontinued until the percarboxylic acid is completely reacted, since insuch case the working up is greatly simplified.

In the event the olefinic compound to be epoxidized forms a minimumazeotrope with'water it is brought in excess amount, into contact withpure aqueous percarboxylic acid in a suitable distillation columnequipped with a water trap in which case a water free solution ofpercarboxylic acid in the unsaturated compound collects in the 'sumpwhile the water in the form of an azeotrope with the unsaturatedcompound is removed in vapor form overhead and after condensation of thevapors in the water trap is separated from the unsaturated compoundwhich latter is again returned to the column.

The invention will be understood best in connection with the drawingswherein the single FIGURE is a diagrammatic illustration of a continuousazeotropic distillation according to the invention.

Referring more specifically to the drawings there is provided adistillation column 1. Percarboxylic acid solution is introduced by wayof conduit 5 and the compound to be epoxidized is introduced via conduit4. The column is also equipped with heat exchanger 6 and thermometer 7.The azeotrope of water and unsaturated compound is led via conduit 10and heat exchanger 9 into water trap 2 whereby after the separation therecovered unsaturated compound is returned to the column via conduit 8while the water leaves the system via conduit 11 and valve 12. Thesolution ofpercarboxylic acid in the compound to be epoxidizedcollecting in the sump of column 1 is withdrawn via conduit 3.

The pressure in the column should be adjusted so that the sumptemperature is the region in which no significant destruction takesplace of the percarboxylic acid employed. Preferably the temperature isbetween 20 and C. but it can be as low as 0 C. or as high as 110 C. Inthe process of the azeotropic removal of water there already takes placea partial reaction to the epoxide. For complete reaction the sumpproduct is subjected to a subsequent reaction at 30 100 C.

In another form of the invention the percarboxylic acids can beextracted from their aqueous solution by the unsaturated compoundsthemselves which are to be epoxidized employing known processes forextraction. Thus there can be used any of the processes disclosed in thearticle in Vauck-Miiller, Grundoperationen Chemischer Verfahrenstechnik,(1966) pages 662, et seq. The entire disclosure of the article in Vauck-Muller is hereby incorporated by reference. After the extraction thesolution of percarboxylic acid in the compound to be epoxidized issubjected to a subsequent reaction at 30 100 C. The extraction, like theazeotropic dehydration, can be carried out continuously or batchwise. Ifthe percarboxylic acid extract still contains small amounts of waterthese can be easily removed by a subsequent azeotropic dehydration, forexample in the manner described above.

The aqueous solutions of percarboxylic acids employed can be used in anydesired concentration of the percarboxylic acid. Preferably they arepure aqueous solutions in the concentrations which are produced, forexample by the processes described in German Pat. No. 1,165,576, GermanAuslegeschrift Pat. No. 1,170,926 and Weiberg US. Pat. No. 3,264,346,e.g., about 40 to 60 percent of lower peralkanoic acid and 60 to 40per-, cent of water by weight although the water can vary from 20 topercent by weight. Examples of suitable percarboxylic acids includeperacetic acid, perpropionic acid, perbutyric acid, perisobutyric acidand pervaleric acid.

The molar proportions of olefinically unsaturated compound to thepercarboxylic acid can be adjusted at pleasure and is not critical.Preferably the proportions range between 1.2 and 25 to l.

The working up of the reaction mixture obtained by the process of theinvention can take place in known manner, for example by distillation orextraction.

As diff culty epoxidizable compounds which can be employed in thedescribed epoxidation process mention is made of the following:

Unsaturated hydrocarbons, (for example diisobutylene, styrene, paramenthene, octadecene-l, nonene- 2, octylene, alpha-pinene, camphene,beta-pinene, stilbene, cycloheptene, alpha carotene, beta carotene,

limonene, dihydronaphthalene, indene, cyclohexene, cyclopentadiene,hepteneal, hexene-l, isoprene,

limonene, p-methyl styrene, l-vinyl cyclohexane), allyl and vinyl esters(for example allyl acetate, allyl propionate, vinyl acetate, vinylstearate, allyl stearate, allyl butyrate, vinyl hexanonate), unsaturatedethers (for example, diallyl ether, 2-metha1lyl ethyl ether, di(Z-methallyl) ether, ethyl vinyl ether, divinyl ether, allyl Z-methylpropen-2-y1 ether, allyl methyl cyclohexen-3-y1 ether, allyl butene-Z-ylether, allyl ethyl ether, allyl cyclopehten-Z-yl ether, allyl vinylether, allyl octyl ether, vinyl methyl ether, vinyl isobutyl ether,allyl methyl ether), unsaturated alcohols (for example 1- buten-3-ol,1-penten-ol-3, cinnamyl alcohol, allyl a1- cohol, crotyl alcohol, oleylalcohol, citronellol, geraniol, linalool, alpha terpineol) and allylhalides (for example allyl chloride and allyl bromide). Generally theunsaturated compounds are liquids so that the percarboxylic acid can bedissolved therein.

The technical advance of the process of the invention first of all is inthe possibility of using percarboxylic acids for oxidation in anessentially safer manner than could be done in the former vapor phaseaddition.

By use of the unsaturated compound itself as the extractant or diluentthe reaction time is sharply reduced because of the increasedconcentration of both the peracid and unsaturated compound compared withthe known processes using solutions of percarboxylic acids in inertsolvents. At the same time the yields are increased over those obtainedwith epoxidation processes with vapor form percarboxylic acids (forexample compare British Pat. No. 1,053,972 Example 6). Additionally theworking up is simplified since besides the unsaturated compound added inexcess and the carboxylic acid arising from the percarboxylic acid nomaterials need to be separated from the reaction product. By theresulting higher space-time-yields the capacity of an existing plant canbe considerably increased and the expense for the apparatus necessaryfor the working up reduced. In carrying out the process in continuousfashion the water free mixture of percarboxylic acid and unsaturatedcompound are completely reacted,

suitably by passing through correspondingly temperature regulatedreaction tubes.

Unless otherwise indicated all parts and percentages are by weight.

The following examples further serve to illustrate the invention.

EXAMPLE 1 A mixture of 500 grams moles) of allyl acetate and- 121.3grams of aqueous peracetic acid (47.7 weight percent peracetic acid,0.75 mol) was azeotropically dehydrated in a vacuum (42 Torr.) in a 1meter Vigreux column having a water trap. The sump temperature of thecolumn did not exceed 36 C. The separated water still contained 0.044mol of peracetic acid which was returned to the column having aninsufficient selectivity capacity. The sump product was subsequentlyheld at normal pressure at a temperature of 50 C. whereby after 12 hoursperacid was no longer detectable in the reaction mixture. By working upwith a vacuum distillation to a maximum bath temperature of 50 C. therewere obtained 67.7 grams of pure glycidyl acetate. This corresponds to ayield of 91 percent of theory based on the peracetic acid.

EXAMPLE 2 1n the apparatus shown in the drawing (effective column height2 meters) 2.5 mols of a 50.8 weight percent aqueous peracetic acidtogether with 8 mols (800 grams) of allyl acetate were dehydrated in avacuum at a sump temperature of 50 C. The subsequent reaction toquantitative peracetic acid reaction took 13 hours at 50 C. By workingup in a distillation there were obtained 258 grams of glycidyl acetatewhich corresponds to a yield of 89 percent of theory based on theperacetic acid.

EXAMPLE 3 In a 50 mm. diameter 2.50 meter long glass column filled withRaschig rings and equipped with a water trap and a return line for theorganic phase separated from the head of the column at normal pressurethere were continuously added hourly between the upper and middle thirdsof the column 127 grams of aqueous peracetic acid (46.9 weight percentperacetic acid, 0.785 mol), and between the middle and the lower thirdof the column 492 grams (6.43 mols) of allyl chloride. The peraceticacid was dehydrated azeotropically. The sump temperature did not exceed48 C. The water separated per hour still contained 0.0024 mol ofperacetic acid. The correspondingly drawn off sump product had aperacetic acid content of about 6.5 weight percent (or 0.47 mol/hour),i.e., there had already occurred about a 40 percent reaction of theperacetic acid.

The sump product was subsequently held in a glass flask for 6 hours withreflux boiling at normal pressure at 50 C. By gas chromatography andtitrimetrical determination of the epoxide in the reaction mixture therewere found 12.8 weight percent epichlorhydrin and by titrimetricaldetermination there was found 0.12 weight percent of peracetic acid.This corresponds to a 98.7 percent peracetic acid reaction and ananalytically detected epichlorhydrin yield of 97 percent of theory basedon the peracetic acid.

EXAMPLE 4 In a 50 mm. diameter extraction column having 30 perforatedplates (20 percent passage) and having an outer mantle cooled to about 5C. there were continuously fed in countercurrent flow 3,000 grams perhour (39.2 mol/hour) of allyl chloride and 407 grams per hour of aqueousperacetic acid (51.9 weight percent, 2.77 mol/hour). The continuouslywithdrawn organic phase (3,160 grams/hour) contained 5.0 weight percentof peracetic acid (2.08 mol/hour), and 0.16 weight percent'water (0.28mol/hour). From 1,000 grams of this mixture (0.66 mol peracetic acid;12.40 mols allyl chloride; 0.09 mol water) there were distilled off in apacked column to remove water as an azeotrope with allyl chloride atotal of 516 grams of allyl chloride and water at atmospheric pressure.The sump still contained 6.5 weight percent (0.415 mol) of peraceticacid, i.e., about 37 percent of the reaction of the peracetic acid hadalready taken place.

The sump product was subsequently held in a glass flask for 6 hours withreflux boiling at normal pressure at 46-50 C. In the reaction mixturethere was found 11.6 weight percent epichlorhydrin (0.605 mol) bytitrimetrical determination and 0.09 weight percent peracetic acid(0.006 mol) by titrimetrical determination. This corresponds to a 99percent peracetic acid reaction and a yield of epichlorhydrin of 92percent of theory based on the peracetic acid.

What is claimed is:

1. A process for the liquid phase epoxidation of a difficultyepoxidizable liquid olefinically unsaturated compound selected from thegroup consisting of olefinically unsaturated hydrocarbons, allyl andvinyl esters, ally] and vinyl ethers, allyl halides and unsaturatedalcohols with an organic peroxide comprising azeotropically distillingan aqueous solution consisting essentially of water, a lower peralkanoicacid having at least two carbon atoms and the compound to be epoxidizedto separate the water from said per acid and then holding the solutionof peralkanoic acid in liquid epoxidizable compound at 30 to 100 C untilthe epoxidation is completed, the molar proportion of olefinicallyunsaturated compound to peralkanoic acid being between 1.2 and 25 to l.

2. A process according to claim 1 wherein the peralkanoic acid isperacetic acid.

3. A process according to claim 1 wherein the olefinically unsaturatedcompound is diisobutylene, styrene, allyl acetate, diallyl ether,2-methallyl ether, 1- buten-S-ol or allyl chloride.

4. A process according to claim 1 wherein the process includesazeotropic distillation at a column pressure such that the sumptemperature is 20 to C.

5. A process according to claim 1 wherein the unsaturated compound isallyl acetate.

6. A process according to claim 1 wherein the unsaturated compound isallyl chloride.

2. A process according to claim 1 wherein the peralkanoic acid isperacetic acid.
 3. A process according to claim 1 wherein theolefinically unsaturated compound is diisobutylene, styrene, allylacetate, diallyl ether, 2-methallyl ether, 1-buten-3-ol or allylchloride.
 4. A process according to claim 1 wherein the process includesazeotropic distillation at a column pressure such that the sumptemperature is 20* to 80* C.
 5. A process according to claim 1 whereinthe unsaturated compound is allyl acetate.
 6. A process according toclaim 1 wherein the unsaturated compound is allyl chloride.